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25 February 2008, Volume 28 Issue 01 Previous Issue    Next Issue

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Dynamics Modeling of Lunar Rover Li Ming Qi Chunzi(Beijing Institute of Control Engineering,Beijing 100080) 2008, 28 (01):  1-8.  Abstract ( 2023 )   Save The dynamics modeling was studied based on the lunar principle rover,and numerical simulations were analyzed.The mechanical properties of lunar soil were explained,and the stresses of driven and towed rigid wheels were analyzed according to terramechanics.The models were simplified to satisfy engineering requirement by using mathematical fitting.In terms of some hypotheses,the 3-DOF dynamics models were analyzed by using Newton-oula method.The interaction of driving and steering of the lunar rover was considered during modeling.The numerical simulation proves the dynamics model is validated. Related Articles | Metrics

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Orbit Dynamics and Control of Satellites Hovering over Space Target Lin Laixing Li Kang(Beijing Institute of Control Engineering,Beijing 100080) 2008, 28 (01):  9-12+34.  Abstract ( 1968 )   Save A successive open loop orbit control strategy suitable to hovering orbit was presented.By implementing a continuous pulse thrust control,the satellite was kept in a period of time on a new hovering orbit other than Kaplan orbit.Finally,taking earth synchronous satellites as a target,the implementation method of hovering orbit was studied,and numerical simulation was also conducted.The simulation results show that it is feasible to hover over special space targets in a period of time. Related Articles | Metrics

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Investigation of Dynamic Parameter Identification of On-orbit Spacecraft Yu Dengyun1 Xia Renwei1 Sun Guojiang2(1 Beijing University of Aeronautics and Astronautics,Beijing 100083)(2 China Academy of Space Technology,Beijing 100094) 2008, 28 (01):  13-17+40.  Abstract ( 1856 )   Save In dynamic parameter identification of on-orbit spacecraft,the modal frequencies are low and high density,the excitation sources are limited and indiscernible.According to these characteristics,a dynamic parameter identification method for on-orbit spacecraft was investigated,directly utilizing on-orbit response to identify the dynamic parameters in frequency domain.It can be used for low and high density frequency identification without excitation information.Considering the characteristic of low and high density frequencies,a simulation test system for dynamic parameter identification of on-orbit spacecraft was developed,which was used to validate the method above. Related Articles | Metrics

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Optimal Control Method for Satellite Formation in Elliptical Orbit Lu ShanXu Shijie(School of Astronautics,Beijing University of Aeronautics and Astronautics,Beijing 100083) 2008, 28 (01):  18-26.  Abstract ( 2056 )   Save A control law for formation keeping was designed using Lyapunov approach,and was optimized by genetic algorithm(GA).Then GA was improved to conquer the disadvantage of weak ability in local optimization.As a result,adaptive simulated annealing genetic algorithm(ASAGA) was developed.The simulation results show that after the optimization,the Lyapunov control law increases the position precision,consumes nearly the same quantity of fuel,and saves the computational time comparing with linear-quadratic regulation(LQR) approach,which is beneficial to implement by on-board computer system. Related Articles | Metrics

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Analysis of Repeatability of the Primary Mirror Deployment Mechanism for Space Optical Remote Sensors Liu Zhiquan Sun Guopeng(China Academy of Space Technology,Beijing 100094) 2008, 28 (01):  27-34.  Abstract ( 2273 )   Save Based on the Hertz contact theory,an analysis method for the repeatability of the primary mirror deployment mechanism was put forward.By this method,the repeatability of the Boyes couplings and Kelvin couplings arranging in two typical modes were analyzed.The analysis results show that the repeat position error of the Boyes coupling caused by the inconsistency of the locking force is less than that of the Kelvin coupling.The repeat position error(absolute value) caused by the inconsistency of the locking force decreases slowly as the diameters of the location balls increase.In the perpendicular direction to the rotation axis of the petal,the repeat position error is most sensitive to the position error of the locking force. Related Articles | Metrics

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Small Scale Heat Balance Test to Verify the Thermal Design of Devices Onboard Spacecraft Jiang Jun Man Guanglong Liu Qiang(China Academy of Space Technology,Beijing 100094) 2008, 28 (01):  35-40.  Abstract ( 1987 )   Save By means of heat analysis and test of a typical device onboard spacecraft,a small scale heat balance test method was introduced to verify the device heat design,so that the repeated whole satellite's heat balance test can be avoided,and just need to verify the changed design of the key device.An equivalence radiation characteristic node and conductive characteristic node were presented to simulate the whole satellite boundary conditions in which the device existed.In addition,a revised model was introduced to analyze the errors resulted under the hypothetic boundary conditions.The rationality and limits of the method were dissassed,and suggestions in application were presented. Related Articles | Metrics

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Simplified Calculation of Regularization of Synthetic Aperture Radar Image Point Target Supper-resolution Yuan Zhenyu1 Wang Zhengming1 Wang Guangxin1,2 Wang Weiwei1(1 Science College,National University of Defense Technology,Changsha 410073)(2 Guilin Air Force College,Guilin 541003) 2008, 28 (01):  41-46.  Abstract ( 2079 )   Save Synthetic aperture radar(SAR) which is a high resolution coherent radar is a significant space remote sensing method,and the resolution of SAR image determines its further application.Regularization method is effective to improve the resolution of SAR image,but the traditional iterative method for resolving the regularization model runs slow.The iterative formulation of image supper-resolution regularization model based on l_k norm was analysed,The analytic expression of the limit of iterative sequence which is produced by the iterative formulation was obtained.According to the conclusion,a new approach to solve the regularization model was obtained,and it could significantly simplify calculation.Simulation and results of MSTAR image processing show that the efficiency of the calculation improves more than 2000 times and the relative error between the presented method and the conventional method is only 6×10-9. Related Articles | Metrics

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Double-hop Downlink Characteristics of GEO Satellite in Deep Space Communication Li Hui Zhang Qinyu Zhang Naitong(Shenzhen Graduate School,Harbin Institute of Technology,Shenzhen 518055) 2008, 28 (01):  47-53+70.  Abstract ( 2336 )   Save Traditional single-hop link is used in deep space communication,which may be greatly affected by kinds of factors in earth's atmosphere.Because of the large difference between the free space link,simply improving carrier frequency can not guarantee the reliability of communication.GEO satellite were used in space as relay station,a double-hop system was constructed from deep space explorer to ground stations,which adopted high frequency in free space link and about 10GHz frequency in the second hop link to evade gases' influences.Comparing with the single-hop system,the double-hop one obtained more ratio of signal-to-noise and channel capacity and less error rate and also improved system reliability.Existing GEO ground antenna's can meet the requirements of the deep space communication missions. Related Articles | Metrics

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Study of Antenna Pointing Servo System Based on Integral Back-stepping Scheme Chu Lixin Lin Hui(Northwestern Polytechnical University,Xi'an 710072) 2008, 28 (01):  54-59.  Abstract ( 2233 )   Save A nonlinear controller based on back-stepping control with integral function was designed.The overall stability of the system was proved using Lyapunov function.Simulation results for the servo-system show that this controller has strong robustness to external disturbance and system parameter changes. Related Articles | Metrics

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Numerical Simulation of Non-continuum Gas Flows with Large Density Variation Zhang Ronghai Yao Wei Li Jindong(China Academy of Space Technology,Beijing 100094) 2008, 28 (01):  60-63.  Abstract ( 1733 )   Save To solve the problem of the simulation of gas flows with large density variation,the multi-region variable time step method was implemented.A remaining time scaling process should be performed for the molecules passing through the interface between two regions with different time steps,thus the continuity of the macroscopic flux across the interface could be maintained.An efficient multi-region interface and surface processing algorithm was presented.It prescribed that each interface belonged to only one region,and the wall surface spanning multi-region was split into a plurality of wall surfaces,each of them belonged to only one region.A simulation molecule could only interact with the interface and wall surface of the region the simulation molecule belonged to.The simulation results of a nozzle flow show that this method can significantly improve the computation efficiency/ Related Articles | Metrics

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Experimental Investigation on Start-up Characteristics of Mechanically Pumped Two-phase Cooling System Liu Jie1 Pei Nianqiang2 Guo Kaihua2,1 He Zhenhui2 Li Tingxun2(1 Institute of Refrigeration and Cryogenics,Shanghai Jiaotong University,Shanghai 200030)(2 Center of Space Technology,Sun Yat-Sen University,Guangzhou 510275) 2008, 28 (01):  64-70.  Abstract ( 1963 )   Save In order to investigate the start-up characteristics of MPLHP(Mechanicalty Pumped Loop Heat Pipe),tests were carried out with different operation conditions. The results show that start-up can cause superheat for the evaporator.Moreover,superheat temperature has little relationship with mass flow and heat load but it depends on evaporative temperature.The less the evaporative temperature is,the higher the superheat temperature is.It was also pointed out that the system designer should pay more attention to the system when system start-up without liquid in the evaporator.Because a larger temperature impact would happen to electrical equipment than the start-up process with liquid work fluid filling with the evaporator. Related Articles | Metrics